The subject invention relates to a pipe insulation system and in particular, to a pipe insulation system that includes a tubular core of fibrous insulation coated with a polymer that is especially well suited for insulating cold pipe systems.
Fiberglass pipe insulation, such as fiberglass pipe insulation marketed by Johns Manville International, Inc. under the trade designation Micro-Lok(copyright) pipe insulation, is a preformed tubular insulation used to insulate pipe ranging in nominal diameter from about 0.5 inches to about 30 inches. The pipe insulation typically comes in 36 inch (0.92 m) long sections with wall thicknesses ranging from about 0.5 inches (13 mm) to 6 inches (152 mm) and in densities ranging from 3 to 6 pcf (0.48 to 0.96 grams/cc). Each pipe insulation section has a first longitudinally extending radial slit extending completely through the tubular wall and a second longitudinally extending radial slit, opposite the first slit, that extends only part of the way through the tubular wall to form a hinge that allows the pipe insulation section to be opened, placed over, and closed about a length of pipe.
These fiberglass pipe insulation sections are typically produced with coverings that are adhesively bonded to the outer surfaces of the sections with an adhesive that typically is a hot melt adhesive. The coverings are typically made of paper-scrim-foil or paper-scrim-MPET where MPET is polyethylene terephthalate with vacuum-sputtered aluminum deposited on at least one surface of the film. The coverings (hereinafter referred to as xe2x80x9cjacketsxe2x80x9d) perform multiple functions:
the jackets contain and protect the fiberglass insulation core;
the jackets generally provide an acceptable finished appearance, i.e. a generally smooth, white matte finish with subtle scrim lines visible through the paper;
the jackets retard water vapor transmission into the fiberglass insulation core, generally with a water vapor transmission test value of 0.02 perms or lower, as tested to ASTM E 96 standard, but do not provide a barrier to water vapor transmission into the fiberglass insulation core; and
the jackets provide a means to secure the pipe insulation to itself with a tape or other mechanical fastener that engages the jacket.
When cold pipe systems are being insulated with these jacketed fiberglass pipe insulation sections or other jacketed fibrous pipe insulation sections, special precautions must be taken to keep water vapor from condensing from the atmosphere onto the cold pipe. ASTM C 755, Section 4.1, states:
xe2x80x9cExperience has shown that uncontrolled water entry into thermal insulation is the most serious factor causing impaired performance. Water entry into an insulation system may be through diffusion of water vapor, air leakage carrying water vapor, and leakage of surface water. Application specifications for insulation systems that operate below ambient dew-point temperatures should include an adequate vapor barrier system.xe2x80x9d
Cold pipe systems are considered to be those systems where the temperature of the fluid in the pipe is between 35xc2x0 F. and 65xc2x0 F. Because ambient conditions in many areas of the United States can commonly result in dew points that are higher than the pipe temperatures, condensation of water vapor can occur in these cold systems. Condensation on the outside of the jacketed pipe insulation sections can contribute to liquid water damage or microbial growth, and condensation on the inside of the jacketed pipe insulation sections can contribute to corrosion of the pipe and a loss of thermal insulation efficiency.
To inhibit condensation from accumulating in these cold pipe systems, the pipe insulation must be installed with a wall thickness sufficient to maintain the outer surfaces of the jacketed fibrous pipe insulation sections warmer than the dew point. If the jacketed fibrous pipe insulation sections do not have sufficient thickness to maintain the outer surfaces of the jacketed fibrous pipe insulation sections above the dew point, condensation will occur on the outside of the jacketed fibrous pipe insulation sections. In addition to the thickness requirement, a water vapor barrier layer [referred to as a xe2x80x9cType Ixe2x80x9d vapor barrier in ASTM C 921-89 (reapproved 1996)] has customarily been used to cover the jacketed fibrous pipe insulation sections to keep water vapor from condensing on the outer surface of the jacketed fibrous pipe insulation and migrating into the insulation where it would condense. Since current jacketed fibrous pipe insulation does not provide a water vapor barrier, if jacketed fibrous pipe insulation is to be installed on cold pipe systems in an unconditioned space, current industry practices recommend that a post-applied layer of PVC (a PVC jacket) be installed over the jacketed fibrous pipe insulation sections to keep water vapor out of the cold pipe insulation system. The PVC jacket must be, sealed with either tape or solvent based welding products. This is the most common way to get a vapor barrier layer that meets the ASTM C 921 Type I standard. However, with this method, the installers must first install the jacketed fibrous pipe insulation and then go back over the entire job a second time to install the PVC jackets over the jacketed fibrous pipe insulation. Thus, this method of sealing cold pipe insulation systems is both expensive and time consuming.
In addition to the need to enclose the jacketed fibrous pipe insulations in PVC jackets when the jacketed fibrous pipe insulations are applied to cold pipe systems, the use of jacketed fibrous pipe insulations may present other problems. While jacketed fibrous pipe insulations generally provide an acceptable appearance, the appearance of the jackets on such pipe insulations can be degraded under certain conditions. The jackets of fibrous pipe insulations are not an integral part of the insulation cores, but, typically, are only bonded to the fibrous insulation cores on each side of the longitudinally extending opening formed in the fibrous cores by the longitudinal slits in the cores. Since the jackets are only bonded to the fibrous cores along the openings formed by the longitudinal slits, rough handling, contact with pipe hangers, butt strip application (joining and sealing adjacent pieces of pipe insulation), etc., may cause deformations in the jackets, such as wrinkling or dimpling, at locations where the jackets are not directly adhered to the fibrous cores. In addition, the absorption of water by some jackets under humid conditions may also cause the jackets to wrinkle or dimple.
The installation of jacketed pipe insulations can also present problems. During the installation of pipe insulation, an installer has to navigate around numerous obstructions such as pipe hangers, valves, elbows, flanges, etc. Normally, the jacketed pipe insulation must be cut to fit the jacketed pipe insulation to the pipe system so that the jacketed pipe insulation accommodates these obstructions. As discussed above, current fibrous pipe insulations have jackets that are adhered to the fibrous cores with lines of adhesive on each side of the longitudinal openings formed by the slits in the fibrous cores. Frequently, these lines of adhesive are not adequate to hold the jackets in place on the cores during and after the cutting of the jacketed fibrous pipe insulations. Some installers resort to stapling the jackets to the cores near the locations of the planned cuts in order to secure the jackets to the cores during and after cutting. This procedure increases the time for installation and breaches the vapor retarding jackets. Sometimes, after cutting pipe insulations, the installer will need to trim the jackets with scissors to provide the jackets with a clean uniform appearance after installation. Again, this extra installation step increases the time required for installation.
Recently, a fiberglass pipe insulation has been introduced that does not block the passage of water vapor, but utilizes a wicking membrane situated around the inside of the fiberglass pipe insulation section. In theory, this membrane is supposed to carry liquid water, which has condensed at the cold pipe surface, back to the outer surface of the pipe insulation section (using capillary action and gravity) where the liquid water is supposed to evaporate. However, these wicking systems are expensive and the installation of these wicking systems requires the exercise of special care. In addition, since liquid water is placed in contact with the outer surface of the cold pipe in these systems, the effectiveness of the system is variable and highly dependent upon ambient temperature and relative humidity. In general, these systems tend to be more effective in low humidity environments and lose their effectiveness in ambient conditions approaching 90xc2x0 F. and 90% humidity.
Alternative pipe insulation systems to fiberglass pipe insulation systems exist for insulating cold pipe systems. The alternatives are mainly closed-cell insulation materials, such as cellular glass, polyisocyanurate foam, rubber, and similar products. However, these products tend to be expensive, time consuming to install, and are prone to installation errors or system breaches.
The subject invention provides a solution to the problem of insulating cold pipe systems by providing a coated fibrous pipe insulation system that in a preferred embodiment does not require an auxiliary outer PVC jacket to provide the system with a water vapor barrier. The coated fibrous pipe insulation of the subject invention does not require stapling to hold the coating in place during and after cutting or the use of scissors to give the coated fibrous pipe insulation a clean uniform appearance after the coated fibrous pipe insulation has been cut during installation. In addition, the coating of the coated fibrous pipe insulation of the subject invention will not be prone to wrinkling or dimpling.
Each pipe insulation section of the coated fibrous pipe insulation system of the subject invention has a tubular fibrous insulation core coated with a pliable or flexible polymer-coating layer that is coextensive with the substantially cylindrical outer surface of the tubular core. The wall of the tubular core has a first longitudinal slit extending completely therethrough and a second longitudinal slit in the inner surface of the tubular core that is substantially opposite the first slit and extends only partially through the wall of the tubular core to form a longitudinally extending hinge in the tubular core that permits the tubular core to be opened, placed over, and closed about a length of pipe. Preferably, the coating layer on the coated fibrous pipe insulation sections of the subject invention as applied to a pipe system has a water vapor permeance rating of 0.02 perms or less and, more preferably, functions as a water vapor barrier. Preferably, the coated fibrous pipe insulation sections of the subject invention are held and sealed about a pipe with an adhesive strip, a solvent weld, or an adhesive material or coating. Preferably, the coated fibrous pipe insulation sections have a thickness and thermal conductivity, for a temperature between 35xc2x0 F. and 65xc2x0 F. at the inner surface of the core and a temperature of 90xc2x0 F. and a relative humidity of 90% at the outer surface of the core, that locates the dew point within the wall of the core at a location spaced from both the inner and outer surfaces of the core wall.